Coaxial transfer switch



Sept. 6, 1966 (5. BOOK 3,271,702

COAXIAL TRANSFER SWITCH Filed Oct. 17, 1960 Q SheetsSheet 1 din/672221":Eric 6. B 0 01 Sept. 6, 1966 E. (5. BOOK 3,271,702

COAXIAL TRANSFER SWITCH Filed Oct. 1'7, 1960 4 Sheets-Sheet 2 .[77 1/6220 7": five 6. B0 015 Jim 4am? Wm Sept. 6, 1966 BQOK 3,271,702

COAXIAL TRANSFER SWITCH Filed Oct. 17, 1960 Q $heetsSheet 3 avzeys Sept.6, 1966 I 3, BOOK 3,271,702

COAXIAL TRANSFER SWITCH Filed Oct. 17, 1960 4 Sheets-Sheet 4 FIE-1E1 yfin; Z0 WM United States Patent 3,271,702 COAXIAL TRANSFER SWITCH EricG. Book, Mokena, Ill., assignor to Andrew Corporation, Orland Park,Ill., a corporation of Illinois Filed Oct. 17, 1960, Ser. No. 63,029 16Claims. (Cl. 333-7) This invention relates to high-frequency switchesand more particularly to a coaxial transfer switch for use at highfrequencies.

A satisfactory transfer switch is required or desirable in various typesof high-frequency systems, for example, where :a transmitter and areceiver are to be simultaneously alternated in connection to twoantennas.

In systems of this type, using coaxial transmission lines operated athigh frequency, it has heretofore been customary to perform suchswitching operations manually, by manipulation of suitable coaxialterminal boards employing coaxial line segments manually manipulated tobridge appripriate terminals, or to use a relatively complex switchingnetwork. Where high-power signals are employed, such solutions to theswitching problem are not completely satisfactory, since the coaxiallines which must be employed to meet the voltage breakdown conditionsimposed by such operation are large and bulky, and the provision ofconventional coaxial switches suitable for the purpose, along with thedummy terminations and similar paraphernalia associated withconventional switching systems employed, is extremely complicated andexpensive.

A practical transfer switch for these purposes, suitable for motorizedor manual operation, has a number of requirements which are achieved ina novel manner in the present invention. It is of course required thatno substantial impedance discontinuity be introduced by the switch, noris any substantial signal attenuation permissible. Since the coaxiallines commonly employed for such uses are gas-filled, the switch isdesirably capable of being isolated from the coaxial lines connectedthereto as regards gas flow, and should itself be capable of beingindependently filled with gas in order to permit maintenance of highbreakdown voltage characteristics without unduly enlarging thedimensions of the switch. Crosstalk between the two signal channelsformed in any switching position must be minimized. In addition, theoverall size of the switch must be held to reasonable limits, and thebulk and complexity of the parts moved in a switching operation mustlikewise be not unduly large in order that the switch can be operatedeither manually or by a motor or relay mechanism of a capacity which isnot excessive.

The above advantages are obtained to a remarkable degree in the switchof the present invention by various features of construction, taken bothindividually and in combination, which are best understood byconsideration of a particular embodiment of the invention incorporatingthe various features of construction which produce the overall result ofprovision of a practical coaxial transfer switch for use over a widerange of frequencies, without undue cost or bulk. Such an embodiment isshown in the annexed drawing, in which:

FIGURE 1 is a top plan view of a coaxial transfer switch made inaccordance with the invention (it being understood that the face of theswitch illustrated, hearing the input and output terminals for theattachment of coaxial lines, is arbitrarily referred to as the top orfront herein for convenience of description, the switch being operablein any position);

FIGURE 2 is a section-a1 view taken along the line 22 of FIGURE 1 in thedirection indicated by arrows;

FIGURE 3 is a horizontal sectional view taken along the line 33 ofFIGURE 2 in the direction indicated by arrows;

FIGURE 4 is a view in end elevation of the rotary or movable portion ofthe switch;

FIGURE 5 is a sectional view taken along the line 5-5 of FIGURE 1 in thedirection indicated by arrows, certain of the parts being shown inelevation and others broken away in section to illustrate theconstruction with greater clarity;

FIGURE 6 is a fragmentary view in end elevation of a switch contactemployed in the construction;

FIGURE 7 is a fragmentary sectional view illustrating the manner ofgrounding the operating shaft of the switch while leaving rotary andreciprocal motion thereof unimpeded; and

FIGURE 8 is a view in section taken along the line 8-8 of FIGURE 7.

The switch is incorporated in a generally square relatively shallowhousing 10, the enclosure of which is completed by a cover or back plate12. The shallow generally square cavity thus formed is of transversedimensions substantially greater than twice its depth, and preferably atleast four times its depth, for reasons to be discussed later inconnection with other aspects of dimensional selection. The cover plate12 is in turn backed by a motor drive housing 14 (shown onlyfragmentarily, since the design of this portion of the illustratedassembly constitutes no part of the present invention) containng asuitable mechanism (not illustrated) for driving the shaft 16 of theswitch in the desired cycle of motion to be later described. The outerend of the shaft is journaled in the top or front face portion 18 of thehousing 10, which is formed integrally with the sidewall 20, forexample, in the form of a single casting. The corners 22 of theswitching cavity are rounded for purposes to be later described.

Bolts 24 and nuts 26 secure the cover plate 12 to the housing 10, a ringseal 27 being interposed at the periphery of the interface. Screws 28secure to the outer face of the front or top of the housing annularflange fittings 30 formed with ferrules 32 and O-ring seats 34, andapertured at 36 to pass appropriate bolts (not shown) into threadedinserts 38 in bores 40 in the front face 18 of the housing for theattachment of the conventional coaxial line outer conductor connectingflanges of the lines 'with which the switch is used.

The top or front face 18 is formed with four large apertures 42 near thefour corners of the square cavity, and concentric with the roundingthereof. Positioned between inwardly facing shoulders 44 and outwardlyfacing shoulders 45 on the abutting surfaces of the flange fitting 30and the front portion 18 of the housing are annular insulator discs 46,in the center of which are fixed contact assemblies generally indicatedby the numeral 48.

Each contact essembly 48 has a coupler bushing 50 having a head 52 atthe inner end, a nut 54 engaging the threaded .stem of the bushing andlocked in position by a set screw 56 and cooperating with the head 52 tosecure-1y mount the bushing 50 in the insulator 56, an O-ring 58 beinginterposed bet-ween the head 52 and insulator 46 to form a gas-tightseal and also to prevent undue strain on the insulator both in clampingof the contact assembly into position and in the operation of theswitch, to be described later. A split or segmented spring connector 60,provided internally wit-h a spreading ring 61, is formed integrally withthe nut 54, serving for the connection of the inner conductor of thecoaxial line (not shown).

A guide rod 62 threaded at the outer end and having thereon a nut andwasher assembly 64 has its shank extending loosely through the bushing50 and is t-hreadedly secured at its inner end to a shallow cup-shapedcontact disc 66, this latter connection being suitably soldered to makea unitary gas-tight construction. A bellows 68, of

suitable metal such as bronze or brass, has its respective ends securelyjoined by silver solder to the head 52 of the bushing 50 and to theperiphery of the contact disc 66. A coiled spring 70 is undercompression between the bushing 52, which is internally recessed at itsinner or lower surface surrounding itscentral aperture to permit the useof an elongated spring 70, and the unitary end contact formed by thedisc 66 and the inner end of guide rod 62. The spring 70 thus urges theinner end of the contact assembly 48 into the interior of the cavity,such motion being limited by abutment of the nut and washer 64 againstthe outer end of the bushing 50 during portions of the cycles ofoperation of the switch in which the inner end of the contact assemblyis not engaged by the rotary contact assembly 72 now to be described.

The rotary contact assembly, generally designated by the numeral 72, ismounted on the shaft 16 by the means of a hub block 74 formed integrallywith an isolating vane 76 which is of a length very slightly smallerthan the square dimension of the housing cavity. As best seen in FIGURE2, the vane 76 is somewhat smaller than the housing cavity in theshallow dimension of the latter to permit small reciprocating motion .ofthe shaft as later to be described. Insulator bars 78 extend throughapertures 80 in the block 7 4 in the direction perpendicular to the vane76, and are secured by bolts 82, the block 74 being slitted at 84between the clamping portions, formed by the intersection of thecircular apertures 80 with the faces of the block parallel and adjacentthereto, and the central vane portion, to permit secure clamping of theinsulator bars 78. The ends of the insulator bars are seated in socket'bores in conductor rods 86 which extend parallel to each other and tothe vane 76 and perpendioular to the bars 78, fastening of the bars 78in the bores being made by pins 88.

I On the ends of the rods 86 are contact members 90 each having a mainor body contact portion 92 and a stem portion 94. The shape of the endportions of the U- shaped bridging members formed by each rod 86 and itsassociated end contacts, as shown in the drawing, may best be understoodfrom a description of the manner in which the assembly is fabricated.Prior to assembly, the end of the rod '86 is a right cylinder, i.e.,merely a rod cut oif from a longer length with a transverse cut. Thestem .portion 94 is originally formed by machining flat surfaces 95 onopposite sides of the cylindrical piece from which the contact 90 isformed. T he upper end of the stem (considering the orientation ofFIGURE 4) is then machined to form a round concavity receiving the rod86. The contact is then secured to the rod by a screw 96 (FIGUREsuitable silver solder also being employed to make a unitary assembly. A45 bevel is then formed on the end of the now unitary rod and stem toproduce a construction for the U-shaped bridging memberin which theshort arms of the U formed by the body portions 90 of the contact are ofgreater diameter than the round adjoining rod 86, the ends of which arebeveled to a 45 angle. The contacting surface of the body portion 92 isformed with a seat 98 beveled between diameters smaller than, andgreater than, the lip of the cupshaped contact disc 66.

The moving contact assembly thus comprises two parallel bridgingcontactshaving contacting ends forming a square coincident with the squareformed by the fixed contact assembly 48. The hub 74 of the rotarycontact assembly is keyed to the shaft 16 at 100 and held in place by anut 102 on the shaft, the end of which is journalled in a bearing 104 inthe front portion 18 of the housing, and the opposite portion of whichextends through a bearing 106 in the cover plate 1-2 into the drivemechanism housing 14. The points of entry of the shaft 16 into theopposite walls of the housing are provided with grounding plates 108 and110 (FIGURES 2, 7 and 8) having spring fingers LIZ-surrounding andcontacting the shaft to ground the shaft, and thus the vane 76, to

the housing. The clearance at 116, provided by the fact that the vane 76does not extend all the Way across the cavity in the small dimension ofthe latter, permits a small amount of reciprocation of the shaft 16 bythe mechanism in the housing 14 as the initial and terminal motions of aswitching operation.

In each operation of the switch, the rotary assembly 72 is firstslightly retracted to disengage the fixed and movable contacts, thenrotated by the outer portions of the movable contacts 90 following thecircular course 118 shown in dotted form in FIGURE 3 of the drawing, andthe outer ends of the vane 76 describing substantially the same path,each 90 rotation reversing the connections of input lines connected toone set of diagonally opposed terminals and output lines connected tothe other diagonally opposed pair. It will be noted, of course, thatsuch a reversal occurs irrespective of the direction of rotation so thatno reversing mechanism is required to be incorporated in the drive meansin the housing 14. For convenience of inspection and servicing, theswitch housing 10 is provided with access ports 120 capped at theirouter ends with suitable removable gas-tight caps (not shown), thediscontinuity in the cavity walls formed by these ports having nosubstantial effect on the electrical performance, for reasons to bedescribed below in connection with certain critical factors ofconstruction. As will be noted in the drawing, suitable O rings areprovided at various interfaces, in addition to those described above, tomake the cavity of the switch gas-tight.

The structural portions of the embodiment illustrated in the inventionhaving thus been described, the purpose and advantages of the variousconstruction features may now be set forth along with the dimensionalconsiderations required in the most advantageous embodiments of theinvention. The external portion of each of the terminals is designed forexact correspondence with the dimensional features of the coaxial lineof the size for use with which the switch is intended. The sealedconstruction as illustrated, and as described above, isolates the gascontent of the cavity from those of the coaxial lines employedtherewith, so that all lines are mutually isolated in this respect fromeach other and from the switch, which may accordingly be operated withany desired gas filling (introduced through ports 120 or otherwise).

The reduced diameter of the inner conductor at the body portion of thebushing 50, and the increased diameter of the inner conductor producedby the shoulders between which the periphery of the insulators 46 isclamped, are compensated by the increase in dielectric constant whichoccurs at this point because of the insulator, so that thecharacteristic impedance of the line at this point continues to matchthat of the coaxial line employed. On the inner side of each insulator,the diameters of the inner and outer conductors again match those of thecoaxial line. The hollow bellows 68 act electrically as solid conductorsat high frequencies because of the skin effect. Loss of continuity atthe interface between the fixed and movable contacts is assured by thecup-shaped construction of the disc 66 and the beveled construction ofthe seating portion of the movable contact, guaranteeing firmness ofcontact at this peripheral portion of the mating, which is the criticalportion, again because of skin effect.

The firm contact engagement is maintained by the spring 70, the yieldingconstruction of the bellows, when coupled with the substantial clearancebetween the guide rod 62 and the aperture in bushing 50 assuringautomatic alignment of the cup-shaped disc 66 and the beveled seatingportion 98 with substantial tolerance in manufacture of all the parts,because of the slight rocking of the disc 66 which will automaticallyproduce full peripheral contact in the event that slight misalignmentshould occur. It will be noted that the bellows 68 forms an importantpart of the gas seal which separates the gaseous medium in the switchcavity from that within the coaxial line attached.

With the contacts seated, the point of joinder is substantially flushwith the front face of the main body of the cavity. At this point, theapertures 42, which form the outer conductors, open into the main bodyof the cavity. In order to preserve the constant impedancecharacteristic, the body 92 of the moving contact 90 is of substantiallylarger diameter than the central conductor of the stationary contactassemblies. The geometry of the transmission system at this pointbecomes of a type incapable of ready calculation of impedance because ofthe complications introduced by more remote portions of the housing, butmay be closely approximated by considering the grounded conductor atthis point as being the adjacent quarter-circle rounding of the cornerof the cavity, which is concentric with the contact. The determinationof the exact size of the enlargement is preferably determinedexperimentally by mismatch or reflection measurements in design ofswitches for various types of coaxial lines.

Adjacent to the contact bodies 92 on the ends of the bridging assembliesare the transition portions whose design for any given impedance, etc.,is best understood by first considering the transmission configurationat the central region of the bridging member. In the seated position ofthe contact, the rods 36 are substantially midway between the wallsdefining the small dimension of the cavity. The dimensioning of thecavity earlier described produces the eflfect that the rods 86 are muchcloser to the walls last mentioned than to the closest adjacent walldefining the square or to the vane. Thus for practical purposes, thetransmission in this portion is substantially in the configuration of awire or rod extending midway between two parallel infinite plates, sothat the design criteria for obtaining any desired impedance in thisregion are known. It will be noted that the difference in effectivedistances just discussed prevents any serious impedance discontinuitydue to the presence of the ports 120, the block 74, or the shaft 16.

The beveled compensation or transformation portions at the ends of therods 86 are designed for the dual purpose of preventing reflections ineach right angle bend in the direction of transmission, and also toprovide transformation between any impedance differences which mayexist, despite care in design, between line impedances in the twodirections of transmission, and compensate for any inaccuracy ofmatching inherent in the fairly complex field shapes. Herea fewexperiments may be required in designing new constructions for optimumoperation, various exact locations of the bevel being employed untilfully satisfactory reflection elimination is obtained.

The vane serves to isolate the two transmission channels formed in anyposition of the switch. It is grounded to the housing through the shaftas previously indicated. This construction is adequate for prevention ofcross-talk between channels at any but the highest of frequencies. Ofcourse, for operation at frequencies at which the leakage past the vanesbecomes intolerable, suitable spring contacts or similar provision maybe made for further grounding of the vane and completion of the barrierbetween the two transmission zones.

From what has been said, persons skilled in the art will be enabled toconstruct a variety of particular designs of coaxial switches,particularly transfer switches, employing the teachings of theinvention, for use with coaxial lines of a wide spectrum ofcharacteristics and details of construction, some embodiments of theinvention obviously being far different in appearance from that hereinillustrated. A typical example of a commercial embodiment of theinvention, made in accordance with the annexed drawing, may neverthelessbe of value as a guide in designing other embodiments. This embodiment,designed for 3%" coaxial line with 50 ohm impedance, has a cavity 9square with a depth of 2.47", the input outer conductor apertures beingslightly over 3" with the annular insulators having an outer diameterslightly under 3 /2" and an inner diameter of .845", the portions of theinner conductor other than that surrounded by the insulator(commercially known as Rexolite) being slightly over 1 1". The movablecontact body is 1.8" in diameter with a thickness of the contactingportion of approximately /6", the width of the stern formed by flattingopposite sides being approximately 1.3" to form a semicircularreceptacle for the bridging rod of the same size. The 45 bevel at theends of the bridging rod (and the stem) terminates approximately halfway between the center and the outer periphery of the upper surface ofthe contact body. The square formed by both the fixed and the movablecontacts is slightly over 5.3 on a side. The vane is slightly over 2" inwidth, thus permitting the motion of the movable assembly desirable forfirmly seating the contacts and also permitting the vane to clear thefixed contacts in the course of operation of the switch, despite thefact that they extend beyond the flush position to a slight degree whennot forced back by the movable contacts. Of course, the clearancerequirement is not high, since the washer and nut stop provided on eachcenter conductor terminal assembly prevents the bellows from extendingsubstantially into the cavity. The embodiment just described produced anisolation between channels of about db at frequencies as high as 480me., with a maximum VSWR of 1.04 over the same frequency range.

As previously indicated, persons skilled in the art will readilyconstruct many embodiments of the invention far different from thatillustrated, but nevertheless employing the teachings of the invention.Accordingly, the invention shall not be considered as limited by theparticular embodiment illustrated, but is defined in the annexed claims.

What is claimed is:

1. A coaxial transfer switch comprising a conducting cavity, a rotor inthe cavity, four coaxial connectors on one face of the cavity havinginner and outer conductors insulatedly supported symmetrically about therotor in the form of a square, two parallel bridging conductors eachadapted to contact a pair of inner conductors forming one side of thesquare and insulatedly mounted on the rotor on opposite sides thereof, aconducting shield on the rotor midway between the bridging conductorsand parallel therewith and extending substantially across the cavitywholly in the region between the bridging conductors, and means forgrounding the shield to the cavity, each bridging conductor forming withthe opposed faces of the cavity and the adjacent side wall of the cavityand the shield a coaxial transmission path isolated from the other bythe shield, each bridging conductor being the inner conductor of acoaxial transmission path and the shield forming only the portion of theouter conductor in the direction of the other bridging conductor, theremainder of the outer conductor of each coaxial transmission path beingdifferent portions of the faces and side walls of the cavity in eachrotary position of the switch.

2. The switch of claim 1 wherein the bridging conductors aresubstantially midway between the inner surfaces of the front and rear ofthe cavity, the spacing between the bridging conductors and the frontand rear being substantially smaller than the spacing between thebridging conductors and the shield and the sidewall of the cavity.

3. A coaxial switch comprising a conducting cavity, a rotor in thecavity, at least four coaxial connectors having outer conductorsgrounded to the cavity and having stationary inner conductorsinsulatedly supported symmetrically about the rotor, at least twobridging conductors each adapted to contact a pair of inner conductorsand insulatedly mounted on the rotor in positions wherein the respectivebridging conductors contact different pairs of inner conductors in eachposition of the rotor, at least one conducting shield on the rotorsubstantially entirely in the region between the bridging conductors andextending from the rotor substantially to the side walls of the cavityto divide the cavity into portions each containing a bridging conductorconductively enclosed only by the walls of the cavity and the shield andforming a transmission path of impedance matched to that of theconnectors, and means for grounding the shield to the cavity, eachbridging conductor being the inner conductor of a coaxial transmissionpath and the shield forming only the portion of the outer conductor inthe direction of the other bridging conductor, the remainder of theouter conductor of each coaxial transmission path being differentportions of the faces and side walls of the cavity in each rotaryposition of the switch.

4. The switch of claim 3 wherein the bridging conductors aresubstantially U-shaped, having contact arms at each end and an elongatedstraight interconnecting conductor, the latter being substantiallyequally spaced from the front and rear walls of the cavity.

5. The switch of claim 3 wherein the bridging conductors aresubstantially midway between the inner surfaces of the front and rear ofthe cavity.

6. The switch of claim 3 wherein the inner end portions of thestationary inner conductors comprise hollow flexible tubular conductivemembers. a

7. In a coaxial switch, a cavity having a rotor therein, a plurality ofcoaxial connectors having outer conductors grounded to the cavity andinner conductors extending into the cavity to form a regular polygonhaving the rotor at its center, a bridging conductor of a length equalto a spacing between inner conductors insulatedly mounted on the rotorto contact pairs of inner conductors, a conducting shield extending fromthe rotor substantially entirely on one side of the bridging conductorsubstantially to sidewalls of the cavity adjacent to the ends of thebridging conductor and shielding the bridging conductor from the portionof the cavity on the opposite side of the shield and rotatable with therotor, and means for grounding the shield to the cavity, the cavitywalls and the shield comprising substantially the sole conductiveelectrical enclosure of the bridging conductor and forming a coaxialtransmission path between connectors.

8. In a coaxial switch, a cavity, a plurality of coaxial connectorshaving outer conductors grounded to the cavity and inner conductorsextending into the cavity, a rotor, a bridging conductor mounted on therotor for selective engagement of inner conductors, a conducting shieldmounted radially on the rotor substantially entirely on one side of thebridging conductor and insulated from the bridging conductor andextending substantially to the sidewall of the cavity, and means forgrounding the shield to insolate the transmission path defined by thebridging conductor from coaxial connectors other than those to which thebridging conductor is connected, the cavity walls and the shieldcomprising substantially the sole conductive electrical enclosure of thebridging conductor and forming therewith a coaxial transmission path ofan impedance matching the connectors.

9. In a coaxial switch comprising a cavity, a coaxial connector havingan outer conductor grounded to the cavity, an inner conductor, andinsulating mounting means receiving the inner conductor in position withits end in the cavity, and a movable contact within the cavity adaptedto contact the inner conductor within the cavity, the improvedconstruction wherein the inner end portion of the inner conductorcomprises a hollow longitudinally flexible bellows having a contactmember on the end thereof and sealed thereto.

10. The coaxial switch construction of claim 9 wherein the cavity has anelongated aperture therein, the outer bellows having therein a springunder compression urging the contact member inwardly and having meansfor limiting extension of the bellows to the region wherein the contactmember is substantially flush with the inner suface of the cavity.

11. The coaxial switch construction of claim 9 wherein the movablecontact and the contact on the end of the bellows have mating outwardlyextending annular surfaces near the periphery thereof, one of thesurfaces being beveled to assure full peripheral contact by deformationof the bellows.

12. A coaxial connector having an inner conductor comprising a hollowflexible conductive tubular enclosure having a contact cap on one endand a bushing on the other end, a spring within the tubular enclosureunder compression between the contact cap and the bushing and a guidemember loosely slidable in the bushing and secured to the contact cap tohold the contact cap in general alignment while permitting slightrocking motion of the contact cap for exact alignment.

1.3. The connector of claim 12 having a stop member abutting the outersurface of the bushing to limit extension of the bellows under theaction of the spring.

14. A coaxial connection having, in combination with an inner conductoras set forth in claim 12, a mating inner conductor in endwise contactwith the contact cap, one of the contacting portions having an annularprotrusion on the edge portion thereof making peripheral contact withthe other.

15. A coaxial switch comprising a hollow conducting cavity, coaxialconnectors terminating in the cavity, bridging members movable withinthe cavity to selectively in terconnect inner conductors of theconnectors and a shielding member substantially entirely between thebridging members and grounded to the cavity, the walls of the cavity andthe shielding member comprising sub bridging members and formingtherewith coaxial trans mission paths of substantially the sameimpedance as the connectors, the shield forming only one portion of eachsuch enclosure, the remainder of each respective enclosure beingdifferent portions of the walls of the cavity in each rotary position ofthe switch.

16. A coaxial switch comprising a conducting cavity of substantiallysquare cross-section, four coaxial connectors dispose-d in the form of asquare on a face of the cavity, a shielding member bisecting the cavityand grounded to the walls thereof, bridging conductors on opposite sidesof the shielding member connecting respective pairs of inner conductorsof the connectors, and a rotary member mounting the shielding member andbridging conductors to reverse the connections of the connectors, thewalls of the cavity and the shielding member comprising substantiallythe sole conductive electrical enclosure of the bridging conductors andforming two coaxial transmission paths of substantially the sameimpedance as the connectors.

References Cited by the Examiner UNITED STATES PATENTS 2,344,780 3/1944Kram et al. 333--97 2,432,476 12/1947 Hesse 200153 2,767,286 10/1956Meth et al 200-153 2,794,087 5/1957 Jennings et al 33397 2,876,4223/1959 Wozniak 333-97 HERMAN KARL SAALBACH, Primary Examiner.

RICHARD M. WOOD, Examiner.

R. K. SCHAEFER, G. TABAK, M. NUSSBAUM,

Assistant Examiners.

3. A COAXIAL SWITCH COMPRISING A CONDUCTING CAVITY, A ROTOR IN THECAVITY, AT LEAST FOUR COAXIAL CONNECTORS HAVING OUTER CONDUCTORSGROUNDED TO THE CAVITY AND HAVING STATIONARY INNER CONDUCTORSINSULATEDLY SUPPORTED SYMMETRICALLY ABOUT THE ROTOR, AT LEAST TWOBRIDGING CONDUCTORS EACH ADAPTED TO CONTACT A PAIR OF INNER CONDUCTORSAND INSULATEDLY MOUNTED ON THE ROTOR IN POSITIONS WHEREIN THE REPSECTIVEBRIDGING CONDUCTORS CONTACT DIFFERENT PAIRS OF INNER CONDUCTORS IN EACHPOSITION OF THE ROTOR, AT LEAST ONE CONDUCTING SHIELD ON THE ROTORSUBSTANTIALLY ENTIRELY IN THE REGION BETWEEN THE BRIDGING CONDUCTORS ANDEXTENDING FROM THE ROTOR SUBSTANTIALLY TO THE SIDE WALLS OF THE CAVITYTO DIVIDE THE CAVITY INTO PORTIONS EACH CONTAINING A BRIDGING CONDUCTORCONDUCTIVELY ENCLOSED ONLY BY THE WALLS OF THE CAVITY AND THE SHIELD ANDFORMING A TRANSMISSION PATH OF IMPEDANCE MATCHED TO THAT OF THECONNECTORS, AND MEANS FOR GROUNDING THE SHIELD TO THE CAVITY, EACHBRIDGING CONDUCTOR BEING THE INNER CONDUCTOR OF A COAXIAL TRANSMISSIONPATH AND THE SHIELD FORMING ONLY THE PORTION OF THE OTHER CONDUCTOR INTHE DIRECTION OF THE OTHER BRIDGING CONDUCTOR, THE REMAINDER OF THEOUTER CONDUCTOR OF EACH COAXIAL TRANSMISSION PATH BEING DIFFERENTPORTIONS OF THE FACES AND SIDE WALLS OF THE CAVITY IN EACH ROTARYPOSITION OF THE SWTICH.